The position indicating transducer of the present invention was specifically developed for use aboard aircraft, for monitoring the position of wing flap or other member. However, it is believed that the transducer has a more general utility in other installations. Therefore, even though reference will be made herein to an aircraft use of the invention, for purposes of describing the invention and its use, it is to be understood that the invention is not limited to aircraft use.
In an aircraft environment, typical position transducers which are used to monitor the position of a control surface or other component of the aircraft include position transmitters, synchros, resolvers, RVTD's (Rotary Variable Differential Transformers). Each of these position transducers produces an electrical signal (usually voltage) that is related (usually proportionally) to the position of their input shafts. This electrical output is used by flight control computers for flight deck indication and for feedback control of the system(s) involved. When not installed in the drive system of the aircraft, these transducers must have their input shafts locked in a specific position to insure that, at installation time, the transducer output will be synchronized to the position of the member to which the transducer is to be connected and whose position it is to monitor.
Various methods have been devised to accomplish the shaft retention described above. These include using lockwire or "rig pins". But, in all cases, the looking component must be removed before the transducer can be installed and coupled to the member whose position it is to monitor. With no input shaft restraint, the correct installation position of the transducer input shaft must be verified electrically prior to installation. This is done by measuring the output voltage of the transducer and comparing it to the voltage required for installation. If incorrect, the input shaft must be rotated until the correct voltage reading is achieved. The transducer is then installed. This process can require several iterations depending on the sensitivity of the transducer and the skill of the aircraft or factory personnel performing the installation.
The principal object of the present invention is to provide a sure and simple shaft-lock addition to the transducer of a type which eliminates the time consuming and error prone removal and adjustment process which has in the past been used. An object of the present invention is to provide a transducer with a lock device which effectively looks the input shaft of the transducer into a synchronized position up until the transducer is mounted and which becomes unlocked, freeing the input shaft for rotation with the member to which it is coupled, in response to the transducer being moved onto its mounting member as a latter stage step of the mounting operation.